36 lines
1016 B
Perl
36 lines
1016 B
Perl
#!/usr/bin/perl -w
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use strict;
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# Declare the variable. It is initialized to the value "undef"
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our $var;
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# Check to see whether it is defined
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print "var contains an undefined value at first check\n" unless defined $var;
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# Give it a value
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$var = "Chocolate";
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# Check to see whether it is defined after we gave it the
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# value "Chocolate"
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print "var contains an undefined value at second check\n" unless defined $var;
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# Give the variable the value "undef".
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$var = undef;
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# or, equivalently:
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undef($var);
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# Check to see whether it is defined after we've explicitly
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# given it an undefined value.
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print "var contains an undefined value at third check\n" unless defined $var;
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# Give the variable a value of 42
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$var = 42;
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# Check to see whether the it is defined after we've given it
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# the value 42.
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print "var contains an undefined value at fourth check\n" unless defined $var;
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# Because most of the output is conditional, this serves as
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# a clear indicator that the program has run to completion.
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print "Done\n";
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