In its most simple case, you could do something like this:

#!/usr/bin/perl

package MyHandle;

sub TIEHANDLE {
    my $class = shift;
    return bless { @_ }, $class;
}

sub PRINT {
    my $self = shift;
    print STDERR "tied PRINT: @_\n";

    # put your implementation here...
}


package main;

tie *STDOUT, "MyHandle";

print "foo", "bar";    # "tied PRINT: foo bar" on STDERR
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(But don't try to print "foo" (i.e. print to the tied STDOUT handle) within the PRINT() method itself — this might do nasty things like segfaulting...)

See Tying FileHandles for how to do it in a more complete way.

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BTW, you could pass further arguments to the tie statement, e.g.

tie *STDOUT, "MyHandle", bar => 'quux';
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These will be passed to the constructor (TIEHANDLE), which it turns into object attributes to utilize for whatever purpose you like. In the example, when dumping $self (using Data::Dumper), you'd then have

$VAR1 = bless( {
                 'bar' => 'quux'
               }, 'MyHandle' );
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