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

my (%patts, $f2_rec, $f2_field);
my $f1 = $ARGV[0];
my $f2 = $ARGV[1];

open(my $fh1,"<", $f1)
    or die "Failled to open '$f1' $!";

while (<$fh1>) {
    chomp;
    next if /^\s*$/;
    $patts{substr $_, 0, 3} = 1;
}

close($fh1)
    or warn "Failled to close '$f1' $!";

open(my $fh2,"<", $f2)
    or die "Failled to open '$f2' $!";

while (defined ($f2_rec = <$fh2>)) {
    chomp $f2_rec;
    next if $f2_rec =~ /^\s*$/;
    $f2_field = (split(/ /,$f2_rec))[1];
    $f2_field = substr $f2_field, 0, 3;
    if(exists($patts{$f2_field})) {
        print "$f2_rec\n";
    }
}

close($fh2)
    or warn "Failled to close '$f2' $!"; # update changing open to close thank to Laurent_R for pointing out

__END__

$ perl test.pl file1.txt file2.txt
ID121 ABC14
ID122 EFG87
ID145 XYZ43
ID157 TSR11
ID181 ABC31
ID529 EFG56
ID684 TSR07