I am trying to understand the behavior of Getopt::Long::GetOptions(), in particulat what happens when user did not supply option values. Refering to my script below :

Cases 1..4 make sense.

Case 5, since the options are required ('='), why does GetOptions() return true? I expected it to fail.

Case 6, since the options are not required (':'), and the documentation says "In this case, if no suitable value is supplied, string valued options get an empty string '' assigned, while numeric options are set to 0.", I expected '' and 0 to be asigned to the variables.

In fact, behavior in cases 5 and 6 is same, while the documentation suggests to me that it would be different.

Can anyone clarify this ?

#!perl -w

use strict;

use Getopt::Long;
use Data::Dumper;
$Data::Dumper::Indent = 0;
$|++;

use Test::More tests => 12;

# using scalars for options

# The option name as specified to the GetOptions() function is called 
+the option specification.
# Later we'll see that this specification can contain more than just t
+he option name.
# The reference to the variable is called the option destination.

# Case 1 from module synopsis
{
    my $data   = "file.dat";
    my $length = 24;
    my $verbose;
    my $result = GetOptions(
        "length=i" => \$length,    # numeric
        "file=s"   => \$data,      # string
        "verbose"  => \$verbose    # flag
    );

    ok($result);
    is( Data::Dumper->Dump( [ $data, $length, $verbose ], [qw / data l
+ength verbose /] ),
        "\$data = 'file.dat';\$length = 24;\$verbose = undef;" );
}

# For options that take values it must be specified whether the option
+ value is required or not, and what kind of value the option expects.

# Three kinds of values are supported: integer numbers, floating point
+ numbers, and strings.

# If the option value is required, Getopt::Long will take the command 
+line argument that follows the option and assign this to the option v
+ariable.
# If, however, the option value is specified as optional, this will on
+ly be done if that value does not look like a valid command line opti
+on itself.

# Case 2
{
    @ARGV = ();
    my $tag = 'deftag';    # option variable with default value
    my $result = GetOptions( 'tag=s' => \$tag );
    ok($result);
    is( Data::Dumper->Dump( [$tag], [qw / tag /] ), "\$tag = 'deftag';
+" );
}

# Case 3
{
    @ARGV   = ('--tag=MYTAG');
    my $tag    = 'deftag';                         # option variable w
+ith default value
    my $result = GetOptions( 'tag=s' => \$tag );
    ok($result);
    is( Data::Dumper->Dump( [$tag], [qw / tag /] ), "\$tag = 'MYTAG';"
+ );
}

# Case 4
{
    @ARGV   = ('--bingo --tag=OTHERTAG');
    my $tag    = 'deftag';                         # option variable w
+ith default value
    my $result = GetOptions( 'tag=s' => \$tag );
    ok( !$result );
    is( Data::Dumper->Dump( [$tag], [qw / tag /] ), "\$tag = 'deftag';
+" );
}

# In the option specification, the option name is followed by an equal
+s sign = and the letter s.
# The equals sign indicates that this option requires a value.
# The letter s indicates that this value is an arbitrary string.
# Other possible value types are i for integer values, and f for float
+ing point values.

# Using a colon : instead of the equals sign indicates that the option
+ value is optional.
# In this case, if no suitable value is supplied, string valued option
+s get an empty string '' assigned, while numeric options are set to 0
+.

# Case 5
{
    @ARGV = ();
    my $tag;
    my $ival;
    my $result = GetOptions(
        'tag:s'  => \$tag,
        'ival:i' => \$ival
    );
    ok($result);
    is( Data::Dumper->Dump( [ $tag, $ival ], [qw / tag ival /] ), "\$t
+ag = undef;\$ival = undef;" );

    # why not a failure, ok(! $result);
}

# Case 6
{
    @ARGV = ();
    my $tag;
    my $ival;
    my $result = GetOptions(
        'tag:s'  => \$tag,
        'ival:i' => \$ival
    );
    ok($result);
    is( Data::Dumper->Dump( [ $tag, $ival ], [qw / tag ival /] ), "\$t
+ag = undef;\$ival = undef;" );

    # why not "\$tag = '';\$ival = 0;" 
}

__END__
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