You are certain to use $pos later in your code; *how* do you use it? Consider looking past the elegance of a single line, toward the elegant interplay within the *paragraph* of code. Your need for a separate $pos variable might even vanish, leaving a Zen-like elegance by its absence.

Some late-night thoughts:

# One-liners; different than the other Monks, but not better.
my $pos = length( (split /\*/, $str)[0] );
my $pos = ( $str =~ m{ \A ( [^*]+ ) }x ) ? length($1) : 0;
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# Get all the positions
my @positions;
push @positions, pos($str)-1 while $str =~ m{\*}g;
# Yields ( 4, 12 );
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# Get all the asterisk-separated pieces
my @pieces = split "\*", $str;
my $pos = length $pieces[0];
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# Just get the first piece
my ( $first_piece ) = ( $str =~ m{ \A ( [^*]* ) }x );
my $pos = length $first_piece;
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