Implements a few useful scalar-related subroutines. Like List::Util, Scalar::Util is something useful that doesn't necessarily fit well as a keyword in the Perl core. By default, Scalar::Util does not export any subroutines. As of Perl 5.8, Scalar::Util is shipped with the source kit.
Scalar::Util implements the following methods.
| blessed |
Evaluates whether expr is a blessed reference. If successful, blessed returns the name of the package. Otherwise, blessed returns undef.
use Scalar::Util qw(blessed); use CGI; my $cgi = CGI->new(); my $not_cgi = "IamNotCGI"; my $is_blessed = blessed($cgi); if(defined($is_blessed) { print "$cgi\n;" } # Prints CGI my $is_blessed2 = blessed($not_cgi); if(defined($is_blessed2) { print "$not_cgi\n"; } # undef
| dualvar |
Returns a string that has the value numberin a numeric context and a value string in a string context. For example:
my $context = dualvar(10, "Nathan"); my $add_nums = $context + 1; # '11' my $str_add = $context . "Patwardhan"; # Nathan Patwardhan
| isweak |
Returns true if expr is a scalar, which is a weak reference:
my $weak_ref = \$boo_hoo; my $i_am_weak = isweak($weak_ref); # false weaken($weak_ref); $i_am_weak = isweak($weak_ref); # true
| openhandle |
Returns fh if fh is an open filehandle. fh may also be a tied filehandle. Returns undef on failure.
my $fh = openhandle(*STDIN); $fh = openhandle("sumfin"); # undef, since sumfin isn't # open
| readonly |
Returns true if scalar is read-only.
| reftype |
Returns the reference type of expr if expr is a reference. Otherwise, returns undef.
my $r_type = reftype "ORA"; # undef, not a reference my $r_type = reftype []; # ARRAY
| tainted |
Returns true if the result of expr is tainted:
my $is_tainted = tainted($ENV{PATH}); # Returns true if -T is enabled
| weaken |
Returns ref into a weak reference. When the reference count on an object reaches 0, ref will be set to undef.
| 8.179. Safe | 8.181. SDBM_File |
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