I don't think you need the longest common substring, but the longest common tail of dirs.

here some code, it basically starts from the end and stops as soon as not all dirs are identical.

(can be done far more elegantly but lost interest ;-)

HTH, TIMTOWTDI!

use strict;
use warnings;

use Data::Dump qw(pp);

my @paths = map { [ split '/' ]  } qw[
        /home/instance/domains/abcd/xyz/1.txt
        /a1234/domains/abcd/xyz/1.txt
        /a1234/topfolder/instance/domains/abcd/xyz/1.txt
         ];
#pp @paths;

my $a_norm = shift @paths;

my @result;
 
dir_loop:
for my $idx ( 1 .. @$a_norm ) {
  for my $a_path (@paths){
    last dir_loop 
      if $a_norm->[-$idx] ne $a_path->[-$idx];
  } 
  unshift @result,$a_norm->[-$idx]
}
 
pp @result;

[download]

output: 

("domains", "abcd", "xyz", "1.txt")

[download]

Cheers Rolf

In reply to Re: Is there any API available in perl to find longest common substring from two strings by LanX
in thread Is there any API available in perl to find longest common substring from two strings by rad_144

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