Assuming the amount of data you are writing to a file is relatively small, another approach is to accumulate the lines of data into an array, then open/write/close the file in one place: 
my @lines;
push @lines, "First line of text.\n";

# keep pushing lines of text into the array

my $filepath = 'foo.txt';
open my $FOOFILE, '>>', $filepath or die "Couldn't open $filepath: $!"
+;
print $FOOFILE $_ for @lines;
close $FOOFILE;

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You could pass the array as a reference to your sub.

In reply to Re: Keep file open for sub call? by toolic
in thread Keep file open for sub call? by zod

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