Jyoti wrote:
Can someone explain me what these symbols mean in regular expression:
my $trim = sub {local($_)=shift;
$$_ =~ s/^\s*//;
^ means that you want to anchor the pattern at the beginning of the
string in $$_. \s is a character class that matches the whitespace
characters " ", "\t", "\f", "\r" and "\n". * is a pattern modifier, it
says that the previous expression (the \s character class) can appear
any number of times in the string, including zero times.
$$_ =~ s/\s*$//;};
$ means that you want to anchor the pattern at the end of the string in $$_.
The use of the * modifier is inefficient as it means that the string is
always modified because every string has zero whitespace at the
beginning and end. It would be better to use the + modifier which would
only modify the string if there is actually whitespace at the beginning
or end.
Also, the use of a reference to the variable stored in $_[0] and the use
of $_ locally in a subroutine seems like a lot of misdirection when the
@_ array is already aliased to the variables passed to the subroutine so
that would probably be better written as:
my $trim = sub {
$_[ 0 ] =~ s/^\s+//;
$_[ 0 ] =~ s/\s+$//;
};
John
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annoyance to those of us who do. -- Isaac Asimov
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