$ perl t.pl

$ cat out.txt 
bob

$ cat t.pl
#!/usr/bin/perl
use strict;
use warnings;

foo("bob");

sub foo {
    my $txt = shift;
    open my $FH, '>', 'out.txt' or die $!;

    bar($FH, $txt);
}

sub bar {
    my ($FH, $msg) = @_;
    baz($FH, $msg);
}

sub baz {
    my ($FH, $message) = @_;
    print $FH $message;
}