If this is only for debugging purpose to find the line numbers , you can close STDOUT and STDERR and cause warnings. But the string to be printed will be lost.

  DB<6> close STDOUT


  DB<7> use warnings; print 666
print() on closed filehandle STDOUT at (eval 15)
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Otherwise I concur with Corion to tie a filehandle. caller will tell you where the tied method was called and you can redirect STDOUT and STDERR to these FHs. (also with select )