Beam_Hystersis( $workbook, $filename, $optsRef );
...
sub Beam_Hystersis {
    my( $workbook, $filename , $optsRef ) = @_;
    use autodie; ## stick this next to use strict so you dont have to keep repeating
    open my($fh), '<', $filename;
    ...;
    $worksheet->write( ... );
    ...;
}