I have two huge files. File1 has one column and File2 has two columns as follows:

File1

ABCD12

XYZ13

EFGT45

UVWZ34

TSR78

........

File2

ID121 ABC14

ID122 EFG87

ID145 XYZ43

ID157 TSR11

ID181 ABC31

ID962 YTS27

ID529 EFG56

ID684 TSR07

ID921 BAMD80

.............

I want to match first column of File1 and starting three alphabets of second column of File2 and print Ids of those are matched.

Desired output:

ID121 ABC14

ID122 EFG87

ID145 XYZ43

ID157 TSR11

ID181 ABC31

ID529 EFG56

ID684 TSR07

I tried foloowing code:

#!/usr/bin/perl
use strict;
use warnings;

my ($f1,$f2,@patterns,%patts,$f2_rec,$f2_field);
$f1 = $ARGV[0];
$f2 = $ARGV[1];
open(PATT,"<", $f1) or die;
@patterns = <PATT>;
chomp(@patterns);
close(PATT) or die;
@patts{@patterns} = (1) x @patterns;

open(FILE,"<", $f2) or die;
while (defined ($f2_rec = <FILE>))
{
    chomp $f2_rec;
    $f2_field = (split(/ /,$f2_rec))[0];
    if(exists($patts{$f2_field}))
    {
    print "$f2_rec\n";
    }
}
close(FILE) or die;
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It know it won't separate matching initial three alphabets, but it will match exact values with 'error: use of unitialized value' until use warnings is blocked. Please help.