Infix operator for string comparison inside expr. Returns true if its arguments are string-equal.
Its opposite part is ne which returns true if its arguments are not string-equal.
Differs from == in such that its arguments cannot be treated as numerical values, so 1 == 1.0 returns true, but 1 eq 1.0 returns false.
Example:
% expr {"a" eq "b"}
0
% expr {"a" ne "b"}
1
%Also comparing text with eq is faster than ==.