foreach/for/while is uncool? Anyway, there's always the trusty goto (adjust regexp to taste):

my $i = 0;
again:
$array[$i] *= 2 unless $array[$i] =~ /[^0-9]/;
goto again if ++$i <= $#array;
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Or as a bare block:

my $i = 0;
{$array[$i] *= 2 unless $array[$i] =~ /[^0-9]/;
 redo if ++$i <= $#array;}
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But I prefer a for:

/[^0-9]/ or $_ *= 2 for @array;
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Why would that not be cool enough?