No, while isn't for. It is optimized to a for(;;) in the case where it is used as while(SOME_TRUE_CONSTANT). It is also optimized away in the case where it is used as while(SOME_FALSE_CONSTANT).

$ perl -MO=Deparse -e 'while (0) {}'
;
-e syntax OK

$ perl -MO=Deparse -e 'while (1) {}'
for (;;) {
    ();
}
-e syntax OK

$ perl -MO=Deparse -e 'while (@_) {}'
while (@_) {
    ();
}
-e syntax OK

[download]

For that matter, even though for and foreach are synonymous, what's in the parens determines how perl actually parses them:

$ perl -MO=Deparse -e 'for (;;) {}'
for (;;) {
    ();
}
-e syntax OK

$ perl -MO=Deparse -e 'foreach (;;) {}'
for (;;) {
    ();
}
-e syntax OK

$ perl -MO=Deparse -e 'for (@_) {}'
foreach $_ (@_) {
    ();
}
-e syntax OK

$ perl -MO=Deparse -e 'foreach (@_) {}'
foreach $_ (@_) {
    ();
}
-e syntax OK

[download]
-sauoq
"My two cents aren't worth a dime.";

In reply to Re^4: grep, map vs. foreach performance by sauoq
in thread grep, map vs. foreach performance by Anonymous Monk

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