оценивать аргументы как выражение (evaluate arguments as an expression)
Обоснование (Rationale)
In an early proposal, EREs were used in the matching expression
syntax. This was changed to BREs to avoid breaking historical
applications.
The use of a leading <circumflex> in the BRE is unspecified
because many historical implementations have treated it as a
special character, despite their system documentation. For
example:
expr foo : ^foo expr ^foo : ^foo
return 3 and 0, respectively, on those systems; their
documentation would imply the reverse. Thus, the anchoring
condition is left unspecified to avoid breaking historical
scripts relying on this undocumented feature.
