```{index} single: IsSTD (B::IO) ``` ```{index} single: B::IO::IsSTD ``` # IsSTD True if this IO is one of the three standard handles. ## Synopsis ```perl $io->IsSTD('stdout') and print "that's STDOUT\n"; ``` Compares the actual `PerlIO *`, so it stays right after a reopen that leaves the glob's name unchanged. Croaks on any name other than `stdin`, `stdout` or `stderr`.