use strict;

my $Usage = "Usage: $0 value file1 file2\n";
die $Usage unless ( @ARGV == 3 and -f $ARGV[1] and -f $ARGV[2] );

my $value = shift;  # removes first element from @ARGV
my $chklen = length( $value );

my @match;  # will hold matching line from each file

for my $file ( @ARGV ) {  # loop over remaining two ARG's
    open( IN, $file ) or die "$file: $!";
    while (<IN>) {
        if ( substr( $_, 0, $chklen ) eq $value ) {
            chomp;
            push @match, $_;
            last;
        }
    }
    close IN; # (this was implicit in the earlier version)
}

print join( " ", @match ), "\n";