ok this program isnt finished, why isnt the filehandle FILE4 being printed out, instead it just erases or overwrites the file being opened

#!/bin/Perl

if (@ARGV < 4) {
    print ("you need to provide 4 arguments\n\t4th argument is file to
+ parse");
    exit;
    
}



openfile(@ARGV);


sub openfile {
    
    open FILE1,">$_[0]" || die "could not open $_[0]";
    open FILE2,">$_[1]" || die "could not open $_[1]";
    open FILE3,">$_[2]" || die "could not open $_[2]";
    open FILE4,"$_[3]" || die "could not open $_[3]";
}


while (my $line = <FILE4>) {
    
print $line;    
}
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