splitting the string with regex - print $2 twice-CodePudding

I have the code:

#!/bin/env perl
use warnings;
$line = 'GFHFHDSH4567 FHGFF           687686';
print $line, "\n";
$line =~ s/  / /g;
$line =~ s/^(. )(?=\s (\d )$)/1:$1\t2:$2/g;
print $line, "\n";

I get:

GFHFHDSH4567 FHGFF 687686
1:GFHFHDSH4567 FHGFF 2:687686 687686

Why it printed twice?

CodePudding user response：

Your regex includes a look-ahead assertion. This doesn't form part of the final matched string, so only the first part of $line, 'GFHFHDSH4567 ', is replaced with the replacement string '1:GFHFHDSH4567 FHGFF 2:687686' The original '687686' is left unchanged.