In
FORTRAN (
IBM,
1956),
= denotes
assignment, and
equality is denoted by
.EQ..
In ALGOL (a largely European design-by-committee effort, 1960), := denotes assignment, and = denotes equality.
Which seems more natural to you depends on which languages you write most fluently. Pascal, being an Algol derivative, uses the Algol convention. C and Perl use Fortran-like conventions.
It's worth noting that John Backus, one of the principal designers of both Fortran and Algol, later came to the conviction that assignment should be banished from programming languages altogether; he founded the branch of programming languages known as applicative or functional languages.