statements exec as expressions when first parameter begins with =

[lmorg]

Describe the bug:
Statements are being executed as an expression when the first parameter is a =

murex » f == bob
cannot EqualTo left Bareword
Expression: f == bob
          :   ^
Character : 3
Symbol    : EqualTo
Value     : ''
murex » f =1 bob
nil symbol following Bareword
Expression: f =1 bob
          :      ^
Character : 6
Symbol    : Bareword
Value     : 'bob'

This doesn't happen if the first character of the first parameter is anything other than =. eg

murex » f== bob
Error in `f==` (0,1): Not a valid expression:
                    >     cannot EqualTo left Bareword
                    >     Expression: f== bob
                    >               :  ^
                    >     Character : 2
                    >     Symbol    : EqualTo
                    >     Value     : ''
                    > Nor a valid statement:
                    >     exec: "f==": executable file not found in $PATH
murex » f >=1 bob
Error in `f` (0,1): flags should begin either with '-' or '+'. Instead got '>'

Expected behaviour:
Statement should be executed as a statement

Platform (please complete the following information):

• OS, output from uname -a if supported: n/a
• Terminal Emulator: n/a
• Murex version, output from version --no-app-name: potentially all in 6.x and earlier