The behaviour can't be changed because of backwards compatibility. The best that can be done is too clearly document the trap, and that has been done. Perl 6, not constrained by backwards compatibility, does allow whitespace before the token.

In reply to Re^3: Can't find string terminator "ENDHEADER" anywhere before EOF by ikegami
in thread Can't find string terminator "ENDHEADER" anywhere before EOF by Anonymous Monk

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