%h=(1 => 2,
    3 => 2,
    4 => 3);

$val = 2;

# use eq for strings, or whatever equals method for objects
@keys = grep {$h{$_} == $val} keys %h; # (1,3)

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Originally posted as a Categorized Answer.

In reply to Re: Get the Key corresponding to any given value by codeacrobat
in thread Get the Key corresponding to any given value by rmalhotra

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