When did it get added to the language?
Pretty sure Perl 1 worked that way so, like, 1987? :)
edit: Yes, so saith the grammar in perl.y from Perl-1.0 
loop    :    label WHILE '(' texpr ')' compblock
            { $$ = wopt(add_label($1,
                make_ccmd(C_WHILE,$4,$6) )); }
...

texpr    :    /* NULL means true */
            {   scanstr("1"); $$ = yylval.arg; }
    |    expr
    ;

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-- Randal L. Schwartz, Perl hacker

The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in RFC 2119.

In reply to Re: while () vs. while (1) by merlyn
in thread while () vs. while (1) by perl5ever

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