while loops
The while
statement repeatedly executes a block as long as its conditional
expression is true. For example:
while (<INFILE>) {
chomp;
print OUTFILE, "$_\n";
}This loop reads each line from the file opened with the filehandle INFILE and prints them to the OUTFILE filehandle. The loop will cease when it encounters an end-of-file.
If the word while
is replaced by the word until,
the sense of the test is reversed. The conditional is still tested
before the first iteration, though.
The while
statement has an optional extra block on the end called a continue block. This block is executed
before every successive iteration of the loop, even if the main
while block is exited early by
the loop control command next.
However, the continue block is
not executed if the main block is exited by a last statement. The continue block is always executed before
the conditional is reevaluated.