#! /usr/bin/perl
# vim:ts=4 sw=4 sts=4 et nu fdc=3:
use strict;
use warnings;

my @str = (
    "bla bla \\mycommand{arg1}{arg2}{arg3} foo foo",
    "Will I work? \\whatever",
    "this will be wrong: \\cmd{arg1} {bad_style_arg}",
);

my $re_command  = qr/\\(\w+)/;
my $re_argument = qr/{([^}]+)}/;

for my $str (@str) {

    # prerequisite: only one command sequenz in $str
    if (   ( my ($cmd) = $str =~ $re_command )
        && ( my @args = $str =~ m/$re_argument/g ) >= 0 )
    {
        print "$cmd with ", scalar(@args), " arguments: @args\n";
    }

}

__END__