perl regex to match a string and add a string next to it

Question

I need to add a string in the middle of some sentences separated by \n. For Example:

INPUT          OUTPUT
V2+count    -> V2+came+count
V6+num      -> V6+came+num
V10+hi+town -> V10+came+hi+town

and

N2+hello    -> N2+went+hello
N7+time     -> N7+went+time

The code I wrote so far is

if ($new=~/\(came\)\|\(went\)/) {
    my $prev_tag = $`;
    if ($prev_tag5=~ /\(V\d+?\)?\+$/) {
        $new=~ s/\(came\)\|//;
    } else {
        $new=~s/\(went\)\|//;
    }
}

All your regular expressions include literal parenthesis, but the examples you have provided doe not include any parentheses, so they would not match any of your regexpes. — pmakholm
– pmakholm, Commented Sep 14, 2012 at 10:22
How should you choose between adding came or went in one specific case? — raina77ow
– raina77ow, Commented Sep 14, 2012 at 10:23
Are the + characters in your data (1) token delimiters — in fact you are working with a list of strings, or (2) whitespaces, you just wanted to emphasize them, or (3) literal plus + characters in the input/output? I am somewhat confused. — amon
– amon, Commented Sep 14, 2012 at 10:28

pmakholm · Accepted Answer · 2012-09-14 10:28:30Z

4

My advise is to keep it simple and not try to handle both cases in parallel. So start by adding 'came' to all the cases matching /V\d+/and then add 'went' to all the cases matching /N\d+/:

$new =~ s/(V\d+\+)/$1came+/;
$new =~ s/(N\d+\+)/$1went+/;

answered Sep 14, 2012 at 10:28

pmakholm

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2 Comments

Kenosis Over a year ago

Although it may be less readable, the two substitutions can be performed on one line using the r modifier: $new = $new =~ s/(V\d+\+)/$1came+/r =~ s/(N\d+\+)/$1went+/r;

pmakholm Over a year ago

More readable, but still one line: $new =~ s/(V\d+\+)/$1came+/;$new =~ s/(N\d+\+)/$1went+/;

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