Just looking at ways to handle cmdline arguments. I know about
getopts but I found this snippet in programming perl book and wanted
to understand better what it is doing.
Probably horribly obvious I guess but what is the s/// operator
(s/^-(?=.)//) in the `ARG:' line doing here:
Also not sure of the significance of ARG: and OPT: labels. (I mean
how it would differ without them)
ARG: while (@ARGV && $ARGV[0] =~ s/^-(?=.)//) {
OPT: for (shift @ARGV) {
m/^$/ && do { next ARG; };
m/^-$/ && do { last ARG; };
s/^d// && do { $Debug_Level++; redo OPT; };
s/^l// && do { $Generate_Listing++; redo OPT; };
s/^i(.*)// && do { $In_Place = $1 || ".bak"; next ARG; };
say_usage("Unknown option: $_");
}
}
Including the brief explanation from Programming perl (Third Ed.)
Here's an example from a real program that uses all three
loop-control operators. Although this particular strategy of
parsing command-line arguments is less common now that we have
the Getopts::* modules bundled with Perl, it's still a nice
illustration of the use of loop-control operators on named,
nested loops:
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