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The exclusive-or operator (^) between strings returns \x00 for each matching pair of characters, and a different value for non-matching characters. Thus, 'Perl' ^ 'Perl' would return '\x00\x00\x00\x00'. Matching a returned string for [^\x00] will show where the strings differ. In your case, only the first difference is requested. Given this, consider the following that uses your data:

use warnings; use strict; open my $fh1, '<', 'first_file.txt' or die $!; open my $fh2, '<', 'second_file.txt' or die $!; while ( my $s1 = <$fh1> ) { chomp $s1; chomp( my $s2 = <$fh2> ); ( $s1 ^ $s2 ) =~ /[^\x00]/; substr( $s2, $-[0], 0 ) = '+' if defined $-[0]; print $s2, "\n"; } close $fh2; close $fh1;

Output:

amaya+mAn vismaya+mAn soura+mA kamal+An

The variable $-[0] contains the position of the last match, which is passed to substr to insert a + at the location of the first difference between the two strings.


In reply to Re^3: partial match between 2 files by Kenosis
in thread partial match between 2 files by lakssreedhar

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