I was not able to run your programme (BTW, is it Estonian?). You should use variable names consistently ($quala is not $q is not $qa).

After fixing the errors, I just removed the square brackets around grep: 

my @output = grep { ! exists $h{$_} } @a;

[download]

Square brackets introduce an anonymous array. You want a list, not an array reference, so no square brackets needed.

لսႽ† ᥲᥒ⚪⟊Ⴙᘓᖇ Ꮅᘓᖇ⎱ Ⴙᥲ𝇋ƙᘓᖇ

In reply to Re: get difference of two arrays by choroba
in thread get difference of two arrays by naturalsciences

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