logevent_is_boringtwisted: break out as a function from LogNotBoringTwisted (nfc)

[hippotat] / subst-sys-path

#!/usr/bin/perl -pi
next unless m{^#\@ };
my $ok = 1;
s{@(\w+)@}{ $ENV{$1} // ($ok=0, $&) }ge;
s{^#\@ }{} if $ok;