This is easy enough - just test each portion individually. When it matches then you know that the current pattern is the one that matched.

sub do_this
{
    my $self = shift;
    my %actions = %{shift()};

    for my $rx ( keys %actions )
    {
        if ( $self->{'find'} =~ $rx )
        {
            print "Found it with '$rx'\n";
            last;
        }
    }
}
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