#!usr/bin/perl -w
use strict;
use 5.10.0;

my @file1 = qw(1GEG
               3RU7
               1BXS
               2JG7
               3QWU
               2BHP
               3ABU);
               
my @file2 = qw(a.1.1.1 1GEG
               a.4.3.5 1BXS
               a.6.7.5 2JG7
               a.8.7.9 2BHP
               a.3.2.1 3RU7);
               
my %file2 = reverse @file2; #swaps pairs! Whoa!

foreach my $fourLetterAcronym (@file1) 
{
   my $value = $file2{$fourLetterAcronym};
   $value //= 'NIL';               #a Perl 5.10 feature
   print "$fourLetterAcronym => $value\n";
}

__END__
Prints:
1GEG => a.1.1.1
3RU7 => a.3.2.1
1BXS => a.4.3.5
2JG7 => a.6.7.5
3QWU => NIL
2BHP => a.8.7.9
3ABU => NIL

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Update: $value //= 'NIL'; #a Perl 5.10 feature
If $value is undefined or "false" in a logical sense set it to "NIL".

In reply to Re: correspondence between two arrays by Marshall
in thread correspondence between two arrays by anasuya

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