Odd subroutine compilation errors in Perl script

Question

Two pieces of ASCII text (one L = long and one S = short) were read into @arrayOne and @arrayTwo, respectively, for comparison. The following subroutine &analyse gets two array references from the smart.pl code, but throws an error when checked via perl -c smart.pl. Unfortunately I can't figure out why:

68  sub analyse {
69      my $arraysize ; my $arrLref ; my $arrSref ; my $item_L ; my $item_S ; my $value ;
70
71      $arrSref = shift ; $arrLref = shift ;
72      $item_S = shift @{ $arrSref } ;
73      $item_L = shift @{ $arrLref } ;
74
75      $arraysize = $#{ $arrSref } ;
76      while ( $arraysize > 0 ) {
77          $value = ( $item_S cmp $item_L ) ;
78          given ( $value ) {
79              when ( -1 ) {
80                  push ( @mergedArray , $item_S ) ;
81                  $item_S = shift @{ $arrSref }
82              }
83              when ( 0 ) {
84                  push ( @mergedArray , $item_L ) ;
85                  $item_S = shift @{ $arrSref } ;
86                  $item_L = shift @{ $arrLref }
87              }
88              when ( 1 ) {
89                  push ( @mergedArray , $item_L ) ;
90                  $item_L = shift @{ $arrLref }
91              }
92              default { &die }
93          }
94      }
95  }

Compilation is aborted with the following statements:

    $ perl -c smart.pl 
    syntax error at smart.pl line 78, near ") {"
    syntax error at smart.pl line 83, near ") {"
    syntax error at smart.pl line 88, near ") {"
    Global symbol "$item_L" requires explicit package name at smart.pl line 89.
    Global symbol "$item_L" requires explicit package name at smart.pl line 90.
    Global symbol "$arrLref" requires explicit package name at smart.pl line 90.
    syntax error at smart.pl line 91, near "}"
    smart.pl had compilation errors.

Maybe someone else has a clue? Thx in advance –DrP-

You have while ( $arraysize > 0 ) { ... Don't you need $arraysize = $#{ $arrSref }; above the second to last }, so the loop terminates, or just while ( $#{ $arrSref } ) { ... and omit $arraysize = $#{ $arrSref }; altogether? — Kenosis
– Kenosis, Commented Dec 8, 2013 at 6:54
Which version of perl your using?Give when statement is available only in perl 5.18.0... — Thiyagu ATR
– Thiyagu ATR, Commented Dec 8, 2013 at 8:00

John Saxton · Accepted Answer · 2013-12-08 06:16:45Z

1

According to the Perl documentation, in order to use given and when, two conditions need to be met:

You need to use feature "switch";
You need Perl 5.10.1+

That should explain what you're seeing on lines 78, 83, and 88.

Regarding the warnings you're seeing on lines 89 and 90, these are tied to the use of use strict;, and an excellent explanation of these warnings can be found here.

edited Dec 8, 2013 at 6:16

answered Dec 8, 2013 at 5:53

John Saxton

5403 silver badges14 bronze badges

Sign up to request clarification or add additional context in comments.

3 Comments

ysth Over a year ago

or do use 5.10.1; (or higher) which will automatically enable features

DrParzival Over a year ago

Thx, but Perl v5.16.2 says "Use of Switch is deprecated." So I chose the given-when syntax. -DrP-

ikegami Over a year ago

@DrParzival, 1) 5.16.2 does not say Switch is deprecated. Perl doesn't know anything about Switch. 2) use feature 'switch' is not use Switch;. As John Saxton said, the former provides given/when. Note that given/when is marked as experimental (and 5.18+ will warn you about this).

Collectives™ on Stack Overflow

Odd subroutine compilation errors in Perl script

1 Answer 1

3 Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

3 Comments

Your Answer

Sign up or log in

Post as a guest

Related