davorg is right. This is a precedence issue.

using 'and' instead of '&&' lowers the operator precedence.

The first one is interpreted as:
print $_ . ("\n" && next) if /no_proc/;

The fixed one is intepreted as:
(print $_ . "\n") and next if /no_proc/;

Note that the brackets include the print statement, not just the parameters.

In reply to Re^2: if modifier of a print statement by tprocter
in thread if modifier of a print statement by si_lence

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