Because it's a here-doc which has nothing to do with Getopt::Long specifically. Search for "<<EOF" in perlop in the section on quote-like operators, but basically it means create a string from everything following this line up to the next line beginning with the terminator string given after the "<<".

The cake is a lie.
The cake is a lie.
The cake is a lie.

In reply to Re: Please explain: print <<"END_USAGE"; by Fletch
in thread Please explain: print <<"END_USAGE"; by richz

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