Beware of prototypes when dealing with functions and named operators. 
$ perl -wle'print sin(0.5) == sub { sin(@_)    }->(0.5) ?1:0'
0

$ perl -wle'print sin(0.5) == sub { sin($_[0]) }->(0.5) ?1:0'
1

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Update: Added code.

In reply to Re^2: trouble taking reference of function by ikegami
in thread trouble taking reference of function by Anonymous Monk

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