use strict;
use warnings;
use OS390::Stdio qw( :CONSTANTS :FUNCTIONS ); 

    my $fh = mvsopen("//'FILE.NAME'", "rb") or die $!;

    my $key = "THIS IS THE KEY";
    my $key_ptr = pack( 'P15', $key );
    
    my $ret = vsamlocate( $fh, $key_ptr, 15, KEY_GE ) or die $!;