Why would you need this:
$s =~ s/^[ \t]+//mg; # remove leading whitespace from each line
$s =~ s/^\s+//; # remove leading whitespace
when the second line will do everything that the firstline is doing?
Remember that
$s is a multi-line string.
So the regex
mg modifier in the first regex above ensures that
each line in the multi-line string has leading spaces and
tabs removed from it.
The second regex, OTOH, does not have any modifiers, so it does not
apply to every line in the multi-line string; instead, it trims leading
whitespace (this time, including newlines) from the front of the multiline string --
trimming multiple blank lines from the front of a multi-line string,
for example.
